1. Field of the Invention
The present invention relates to a semiconductor light emitting apparatus, an image displaying apparatus, a mobile terminal, a head-up display apparatus, an image projector, ahead mounted display apparatus, and an image forming apparatus.
2. Description of the Related Art
An existing semiconductor light emitting apparatus employs a plurality of light emitting diodes (LEDs) arranged in a one dimensional matrix or a two-dimensional matrix, each LED functioning as a minimum unit of an image, i.e., pixel. For example, the LEDs are integrated on a substrate, and are connected to wirings as first common electrodes and wirings as second common electrodes formed on the substrate. Each chip of LED is at a corresponding pixel position. One way of increasing light power of these LEDs is to increase the amount of injected current. However, larger currents flowing through the LEDs and the first and second wirings will seriously increase heat generated due to electrical resistances thereof. An increased amount of heat causes a decreased internal quantum efficiency of LED chips. Therefore, minimizing heat generation and dissipating heat efficiently are important factors in preventing temperature rise in the apparatus. Japanese Patent Publication No. 2002-278481 proposes a method for efficiently dissipating heat generated in a semiconductor light emitting apparatus. That is, a heat conductive material is prepared by kneading silicone rubber or epoxy resin with a metal oxide in powder form such as aluminum oxide or iron oxide, and is applied to the LED chips in intimate contact, thereby efficiently dissipating heat generated in the semiconductor light emitting apparatus.
However, the method disclosed in Japanese Patent Publication No. 2002-278481 suffers from the following drawbacks. If the light emitting chips have not a sufficient thickness or the surface of the light emitting chips has very good wettability, the heat conductive material climbs up to the upper surface of the light emitting chips, thereby blocking the light emitted from the light emitting chips, hence a decreased light extraction efficiency. The heat conductive material is usually applied using a dispenser. If the light emitting chips are densely integrated, the dispenser is required to dispense the heat conductive material very accurately. This increases the complexity of the manufacturing process, possibly decreasing the yield of the products.